Gorf sound effects missing <FIXED>

[beankp60]

A bit of background
I have owned my Gorf machine since 2012. When it arrived it was in a bit of a state with no signs of life. I had to repin and replace most of the loom connectors as the machine had been modified to run something else at some point. Also the power board was rebuilt with Bob Roberts kit. The monitor chassis boards needed a bit of work too.
When it first landed
IMAG0649 by Bean Beano, on Flickr

Eventually the machine came to life and with alot of board swapping about and a few roms replaced i was playing Gorf again.

I came to play the machine a few days ago and it was not playing, after messing about i got the machine working again.

The sound fault

One of the issues i never resolved since ive had the machine is i only ever had one channel of the audio. if i watched gorf footage on youtube i have alot of the sounds missing like when the invaders move or the lazers fire on one of the levels ect.

I have replaced most of the components on the audio amp board including the Kemet cap which blew at some point and also the 2 resistors with it. Also the 2 Tip31 transistors. I have also swapped my CR1 and CR2 piggybacked components over to try if that got my other channel working but it didnt make any difference.
I have reconnected the J1 jumper to switch the audio board to mono and i get good sound through both speakers and both pots adjust both speakers fine so i know my speakers and wiring to the speakers is good.

Gorf audio amp board by Bean Beano, on Flickr

Gorf audio amp board by Bean Beano, on Flickr

After reading this thread by Scottacus http://forum.arcadecontrols.com/index.php?topic=144043.0&fbclid=IwAR3AE5vRu5aBEfwV_HvaRIBNZiWJMzad1CSyAlCrzBkR39nSAxhG_sbuKL8
Which had some great info i thought i should try swapping the X2 and X3 chips but it never made any difference to the fault. I have checked the pins from the gameboard to the audio amp board and they are all correct.

I have 3 different game boards and i get the same sound issue with all of them. If anyone has any ideas they would be much appreciated.

Cheers

Paul

[jennifer]

I would at this point be pulling my hair out...However, that slide switch seems suspicious to me, the mechanical nature of it is prone to failure, if not the switch itself, the connections to the board.

[Scottacus]

Sorry to hear about your problems!

I'm not an electronics expert and on my Gorf Game I had only half of the sounds coming out.  It turned out to be a bad 0066-117xx in X3 with a good one in X2.  I found that the game would run with a bad chip in X3 but not in X2 so I was lucky that the fault was there!  I'd compare the sounds that you are missing to the ones that I listed in my post mentioned above and see if they match up.  If they do then the problem lies along that pathway somewhere.

If it is a bad 0066-117xx good luck finding one.  Perhaps you can just buy a board on E-Bay and swap it out to see if that fixes your problem?  They can be pricey but it is nice to have a spare set just in case something fails (which it will) in the future...

[beankp60]

I would at this point be pulling my hair out...However, that slide switch seems suspicious to me, the mechanical nature of it is prone to failure, if not the switch itself, the connections to the board.

The switch seems to be working fine. There seems to be some sort of corrosion around the pins so maybe i could remove all the solder and resolder them.

[beankp60]

Sorry to hear about your problems!

I'm not an electronics expert and on my Gorf Game I had only half of the sounds coming out.  It turned out to be a bad 0066-117xx in X3 with a good one in X2.  I found that the game would run with a bad chip in X3 but not in X2 so I was lucky that the fault was there!  I'd compare the sounds that you are missing to the ones that I listed in my post mentioned above and see if they match up.  If they do then the problem lies along that pathway somewhere.

If it is a bad 0066-117xx good luck finding one.  Perhaps you can just buy a board on E-Bay and swap it out to see if that fixes your problem?  They can be pricey but it is nice to have a spare set just in case something fails (which it will) in the future...

Hi Scott thanks for checking my post out. I actually have 3 complete board sets so ive plenty of parts for now.
Im sure i tried swapping the x2 and x3 chips around but it made no difference. I will double check that though.

The sounds i have missing are the ones when the invaders move (like a drum beat) and the lazer fires on the lazer attack stage and i bet there are others i havent noticed yet. Im going to have another read through your thread and try get a better understanding of whats going on here.

Gorf stereo audio board by Bean Beano, on Flickr

I thought about swapping pins 4 and 6 over going to the sound amp board to see if it gives me the audio channel i am not getting so atleast then i would know it is getting to the sound amp board or not.

[beankp60]

Right so i have sound on Pin 6 but i have no sound getting to pin 4 on the audio amp board on a yellow green wire which is fed from pin 2 of the larger connector on the game board. I gues i need to work my way back through that line and see if i can find anything.

[Scottacus]

I was missing the sound effects for Galaxians falling, space invaders stomping, laser ships shooting...

[beankp60]

it sounds like i am missing the same channel.

Ive traced the pin from the audio amp to the custom chip and no brakes or anything there. ive not tested the resistors and transistors yet.

Ive also gave mark spaeths test program a go and i am having some issues with that. It is saying i need to check chip U21 which is on the game board. Ive have tested all 3 game boards i have and they all say to check U21 so i might have an issue there i need to look into also. I think ive got a bit of learning to do.

[beankp60]

Just fixed this.

I was double checking the loom between the game board pins and the audio board. I had been testing from game board pin to the connector pins on the audio board. I tested onto the actual amp board solder side pins and i had no connectivity. I looked at the connector and the back half of the pin had fell off. I repinned this loom in 2012 so no idea when this happened. But for the first time since ive had the machine I heard the invaders moving sounds. Im just now going to cut the jumper wire on the amp board to put it back into stereo mode and then i should be sorted! Thanks for the help. A lesson learnt for me here to test onto the board and not just the pin in the connector. Time to play some stereo Gorf!

[Scottacus]

Congrats, nice job sticking with it and finding the problem!  Sometimes the problem is just something mechanical like a broken pin.  In the world of pinball the problem is often times (95 out of 100) a mechanical problem (switch contact, broken wire, bad solder joint) and not something complex like a bad chip.